Yes. That sounds like the same increments that my feeler gauge set has. The rule with feeler gauges is that the measure of the gap is at least as large as the thickest feeler gauge that will fit into the gap without interference (any contact) and less than the next thickness gauge that has interference. As you have surmised, a feeler gauge is not a precision measurement tool. However, there are few alternatives in this application.
The imprecision of the measurement is the reason that I set the gap of the valve shims to be the next smallest gauge size than the nominal thickness. With the gauge set that we have, I calculate and install a shim for the intakes that allows the .178mm gauge to fit without interference, but not the .203mm gauge. For the exhaust valves, I shoot for the .279mm gauge t fit, but not the .305mm gauge.
The nominal values are .20mm for the intakes and .30mm for the exhausts with a range of plus or minus .05mm around each of those points. The method I use ensures that the gap is between the nominal thickness (intake example .203mm) and one feeler gauge thickness less (ex. .179mm), but larger than one full gauge size above the minimum (ex. .15mm). This allows for at least the design amount of valve lift and still maintains a clear margin for error on the small side.
There are engineering justifications for setting a range, the nominal (center) value is the manufacturer's ideal setting. This accounts for impact energy, valve lift and duration and thermal expansion of the component parts (among others). You can't set the gap to less than the minimim thickness without the risk of not letting the valve seat under full spring pressure. This could cause loss of compression and power under conditions where the valve is not seated and valve seat erosion if the seat pressure is not sufficient to contain the combustion pressures.
I hope this gives you a valve lifting experience.
any insight on the feeler gauge though
